Adding Frontmatter Reader: Support summary card (OG. Twitter) by sspaeti · Pull Request #2321 · rust-lang/mdBook

sspaeti · 2024-02-20T16:55:20Z

See issues #1416 and specific description in my comment: #1416 (comment).

This works for my site dedp.online, but I'd appreciate some help to integrate it nicely. It's more hackable and hard-coded to these frontmatter I used:

struct FrontMatter {
    title: String,
    description: String,
    featured_image_url: String,
}

Would be nice to read them dynamically. Also, I'm not sure if I added it at the right points.

PS: I also tried to implement a preprocessor (see #1416 (comment)), but with this PR that one is not needed anymore. Also, I guess this should be integrated into mdBook, and can't be as Preprocessor only?

szabgab · 2025-04-03T16:12:53Z

Hi, would you have time to rebase this to make it easier to review it, please?

szabgab · 2025-04-03T16:14:47Z

 toml = "0.5.11" # Do not update, see https://github.com/rust-lang/mdBook/issues/2037
 topological-sort = "0.2.2"
+gray_matter = "0.2" #Fronmatter
+serde_yaml = "0.9"


serde_yaml was deprecated recently, please use serde_yml

szabgab · 2025-04-03T16:33:48Z

+use serde::Deserialize;
+
+fn extract_frontmatter(content: &str) -> Option<&str> {
+    let start = content.find("---")? + 3; // Find the end of the first `---` + 3 to move past it


Given that --- can appear anywhere in a regular markdown content, I'd restrict this to the case when the file starts with ---.

Adds a `frontmatter` feature flag that parses YAML frontmatter from chapter content and injects OG/Twitter meta tag data into the Handlebars template context. All custom code is isolated in a single module (frontmatter.rs) with 3 one-liner integration points behind #[cfg(feature = "frontmatter")] for easy future upgrades. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sspaeti · 2026-02-12T21:40:23Z

@szabgab I finally updated my book, and therefore also rebased this branch.

The pre-processor https://github.com/sspaeti/mdbook-frontmatter-reader is no longer needed and has been integrated directly into frontmatter.rs (see changes).

Again, in my chapters in my mdbook, I can now add this in the frontmatter

---
title: "Business Intelligence, Semantic Layer, Modern OLAP, Data Virtualization"
description: "The history of semantic SQL"
featured_image_url: "https://www.dedp.online/images/features/ce-semantic-sql.png"
---

and that gets rendered in the HTML header:

FYI, if anyone is doing similar things - I added these hard-coded to my index.hbs as these do not change:

  Meta tag: <meta name="author" content="Simon Späti">
  Meta tag: <meta property="og:type" content="book">
  Meta tag: <meta name="twitter:card" content="summary_large_image"/>
  Meta tag: <meta name="twitter:creator" content="@sspaeti"/>

You can check the outcome in my book live at https://dedp.online/part-2/4-ce/semantic-layer-business-intelligence.html.

I hope that works, not sure if I have thought about everything, as this is my first mdBook submission, but it works great for my book for a long time :)

Update: You also need to update index.hbs with something like - see initial comment at #1416 (comment):

<head>
...
        {{#if is_frontmatter }}
        <meta property="og:title" content="{{ og_title }}">
        <meta property="og:type" content="book">
        <meta property="og:image" content="{{ og_image_url }}">
        <meta property="og:url" content="{{ base_url }}">
        <meta property="og:description" content="{{ og_description }}">
        <meta name="author" content="{{ author }}">
		..dynamically read what's defined in frontmatter?..
        {{else}}
        <!-- Add static Open Graph Meta Tags for Social Media Exposure -->
        <meta property="og:title" content="Data Engineering Design Patterns: Mastering Convergent Evolution">
        <meta property="og:type" content="book">
        <meta property="og:image" content="https://www.dedp.online/static/og-image.png">
        <meta property="og:url" content="https://www.dedp.online">
        <meta property="og:description" content="A data engineering book to understanding design patterns, exploring the concept of convergent evolution and its significance.">
        <meta name="author" content="Simon Späti">
        {{/if}}
...
</head>

This reverts commit 916cb56.

ObserverOfTime · 2026-05-30T13:26:47Z

I tried this PR but don't see any tags in the generated HTML. Do I have to modify index.hbs in some way?

Also, serde_yml is unsound and unmaintained and should be replaced.

sspaeti · 2026-07-06T06:37:53Z

I tried this PR but don't see any tags in the generated HTML. Do I have to modify index.hbs in some way?

Also, serde_yml is unsound and unmaintained and should be replaced.

Yes, you need to add it to index.hbs see initial comment #1416 (comment), or what I have at this moment:

        <!-- Open Graph Meta Tags for Social Media Exposure -->
        {{#if is_frontmatter}}
        <meta name="title" property="og:title" content="{{ og_title }}">
        <meta name="description" property="og:description" content="{{ og_description }}">
        <meta name="twitter:title" content="{{ og_title }}"/>
        <meta name="twitter:description" content="{{ og_description }}"/>
        {{else}}
        <meta name="title" property="og:title" content="Data Engineering Design Patterns: Timeless Practices for Data Engineers">
        <meta name="description" property="og:description" content="A data engineering book to understanding design patterns, exploring the concept of convergent evolution and its significance.">
        <meta name="twitter:title" content="Data Engineering Design Patterns: Timeless Practices for Data Engineers"/>
        <meta name="twitter:description" content="A data engineering book to understanding design patterns, exploring the concept of convergent evolution and its significance."/>
        {{/if}}
        {{#if og_image_url}}
        <meta property="og:image" content="{{ og_image_url }}">
        <meta name="twitter:image" content="{{ og_image_url }}"/>
        {{else}}
        <meta property="og:image" content="https://www.dedp.online/static/og-image.png">
        <meta name="twitter:image" content="https://www.dedp.online/static/og-image.png"/>
        {{/if}}

        <meta name="author" content="Simon Späti">
        <meta property="og:type" content="book">
        <meta name="twitter:card" content="summary_large_image"/>
        <meta name="twitter:creator" content="@sspaeti"/>

ObserverOfTime · 2026-07-06T07:26:02Z

Shouldn't that be part of the PR? :)

sspaeti · 2026-07-06T07:57:40Z

Shouldn't that be part of the PR? :)

You are probably right! I just added it e944348 (not tested with plain mdBook yet, but should work, hopefully) - I didn't add it initially because I thought index.rbs is to be customized by each book, but I saw there's a template. I think the above comment would make sense.

rustbot · 2026-07-06T08:09:58Z

This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

sspaeti · 2026-07-06T08:13:50Z

+        <meta property="og:image" content="{{ og_image_url }}">
+        <meta name="twitter:image" content="{{ og_image_url }}"/>
+        {{else}}
+        <meta property="og:image" content="https://avatars.githubusercontent.com/u/5430905?s=48&v=4">


Please note I added the Rust logo from mdBook GitHub icon - please add or link a mdBook icon that you want to be shown on social media, if there's one. This is the image that will be shown when sharing online. As well as the line below twitter:image.

View changes since the review

rustbot added the S-waiting-on-review Status: waiting on a review label Feb 20, 2024

sspaeti mentioned this pull request Feb 20, 2024

Feature request: Support summary card (Twitter, WhatsApp, ..) #1416

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sspaeti mentioned this pull request Mar 11, 2024

Metadata on a per-page basis #2142

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szabgab reviewed Apr 3, 2025

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sspaeti and others added 3 commits February 12, 2026 20:38

add Makefile back

c749ea4

update serde_yml

c3e8b00

sspaeti force-pushed the adding_frontmatter branch from 4777b3a to c3e8b00 Compare February 12, 2026 21:17

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remove personal makefile

89ac94b

sspaeti requested a review from szabgab February 12, 2026 21:44

sspaeti added 2 commits February 27, 2026 23:37

add created date and last updated date to front matter

916cb56

Revert "add created date and last updated date to front matter"

0a193ef

This reverts commit 916cb56.

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adding open Graph meta tags to templage index file

e944348

sspaeti added 2 commits July 6, 2026 10:09

Merge branch 'master' into adding_frontmatter

5153b31

merge master

42273c4

sspaeti commented Jul 6, 2026

View reviewed changes

fix: test error with property="og:description"

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Adding Frontmatter Reader: Support summary card (OG. Twitter)#2321

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